This invention relates generally to unwind devices and feed controls which are used for unwinding highly elastic and tacky threads from a spool/package of such thread, and feeding such threads into a manufacturing process which uses and/or further processes such threads.
In general, a spool/package of the desired thread is mounted on an unwind stand. Thread from the spool/package is threaded by hand into the manufacturing process at process start-up. As the manufacturing process which uses the thread proceeds, thread is pulled from the package and guided to the manufacturing process.
One method of unwinding and feeding thread from a spool of such thread in manufacturing processes is referred to as a “rolling unwind”. In the rolling unwind method, the package/spool is mounted in an unwind stand with the axis of rotation of the package/spool oriented generally perpendicular to the direction in which the thread is to be drawn from the package. The spool/package turns at a speed which is related to the unwind speed, allowing for a desired feed rate, so as to feed the thread from the rotating package along a line which generally approximates a perpendicular to the axis of rotation of the spool of thread and which is generally tangent to the outer surface of the thread on the spool.
When a first package of the thread is exhausted, the manufacturing process is shut down. The first package is removed. A second package is installed and threaded up.
A major disadvantage of a rolling such unwind operation is that the manufacturing process must be shut down every time a spool of thread is exhausted. Since the manufacturing process typically draws a plurality of material feeds from a plurality of source packages of thread, shutting down the entire manufacturing process when a single source is exhausted typically results in substantial down-time losses and substantial production of scrap during shut-down and start-up. Accordingly, in one method of controlling the amount of down-time, when one roll has been exhausted and the process is shut down, all rolls relating to that process are replaced with full rolls irrespective of the amount of thread remaining on a given spool. The result is the wasting of the thread which remains on those spools which are not exhausted.
Another method of unwinding and feeding thread from the spool is known as the overend take-off method (OETO). In the overend take-off method, the package of thread is fixedly mounted on the unwind stand so that the axis of rotation of the package is pointed in the general direction of the path to be traversed by the thread as the thread is drawn from the package. However, in the overend take-off method, the package of thread does not rotate as the thread is being drawn from the package. Rather, the thread comes off the spool over the end of the spool. As the thread leaves the spool, the locus of departure rotates about the circumference of the spool, such that the path initially traversed by the thread is rotational in nature. At lower speeds, the thread gets just past the 12 o'clock position on the spool and drops to the 6 o'clock position. At higher speeds, the thread rotational action embodies centripetal forces which are acting essentially perpendicular to the general direction of travel of the thread, whereby the thread leaving the spool looks much like a loop, a jump rope, or hoop, or ballooning action. All such actions are intended to be included in referring to the action of the thread as a “loping” action. Such loping action must be controlled, damped out, so that the thread can be guided at controlled tension and direction along a predetermined path, in such a manner as to be delivered, fed, to the manufacturing process at a controlled and generally constant, though changeable, level of tension. In achieving the generally constant level of tension, the tension spikes and other tension variations, which are inherent in the overend dispensing of such a sticky thread, must be dissipated within the unwinding and feeding mechanism.
Since the spool is fixed in location, the operator can tie the trailing end of a first active spool to the leading end of a next-in-line reserve spool such that the tail end of an active spool automatically transfers the feed to the reserve spool when the active spool is exhausted, whereby there is no need to stop the manufacturing process to change spools. Accordingly, overend feeding inherently avoids the above-noted wasting of thread on changed-out spools where the thread supply has not all been used up, as well as the shut-down, start-up times associated with such spool change-outs Thus, overend feeding embodies built-in cost savings related to both materials usage and production output, whereby overend unwinding is a desirable technology for unwinding tacky threads and feeding such tacky threads into a manufacturing process.
However, overend unwinding and feeding technology has its own challenges to successful operation. In conventional overend unwind technology, the thread coming off the spool is first fed through a circular ceramic eye to suppress the jump rope, hoop, ballooning characteristic of the thread coming off the spool. In a creel which supports and controls a plurality of simultaneously-active threads, each thread is initially fed through a separate such circular ceramic eye, and the threads are fed from the initial circular ceramic eyes to a common driven roll. The driven roll treats all of the threads the same. Namely, each thread passes over, through its own groove on the driven roll, whereby all of the threads are individually treated to a common roll drive and/or retardation.
The purpose of such driven roll is to capture and eliminate laterally-directed kinetic energy in a thread and to absorb and eliminate longitudinally-directed force/tension variations in the thread. Tension both before and after the driven roll can vary widely depending on winding tension in the spool, as well as the experience of the thread between the spool and the driven roll. The result is that thread speed is controlled at the driven roll, while tension continues to vary from thread to thread in a given unwind operation on an unwind stand. But there is no sensing, no direct control, of the tension in individual ones of the threads leaving the driven roll. Nor is there any sensing, any direct control, of the tension in the collective combination of the threads leaving the driven roll. And there is no control of tension in the threads between the driven roll and the manufacturing nip where the threads enter the product assembly operation.
Still referring to conventional overend technology, from the driven roll, the threads make their ways, along pre-determined paths, to respective entrance points into the manufacturing process. Given the layout of a typical manufacturing line for personal hygiene products where such threads are commonly used, there is commonly no space for the unwind creel immediately adjacent the point of entry of the threads into the manufacturing process.
So a common location for the unwind creel is across an aisle or walkway from the manufacturing process line. Thus, the distance which the thread travels, from the driven roll on the unwind creel, to the point of entry at a nip in the manufacturing process, is several meters, typically about 10 meters. Further, each thread passes over a number of turning rolls and guides in traversing along the thread path, from the unwind creel to the manufacturing process, including across the aisle/walkway. In such traversing, each thread passes over a separate and distinct set of guides and rolls, separate and distinct from the set of guides and rolls traversed by any other thread.
Each such turning roll or guide adds a measure of tension to the respective thread. By the time the thread gets to the process nip, the tension in the thread has been changed by its contacts with the respective guides and rolls, such that the tension on a given thread entering the nip at the manufacturing process is different from the tension on that same thread as the thread leaves the driven roll on the creel. Further, the tension increment at each such guide or roll is different depending on surface characteristics of that guide/roll, efficacy of the bearings if any, any dirt or lubricant which may have accumulated on the surface of the guide or roll, any dirt or other detritus which may have gotten into roll bearings, or the like. Overall, in conventional overend technology, the tension entering the manufacturing nip is not well controlled by controlling the speed or tension at a driven roll which is close to the elastic fiber spool and relatively farther from the manufacturing nip.
A further problem with conventional unwind systems is that the ceramic eye, which is first encountered by the thread as the thread leaves the spool, is motionless, and thus exerts a static friction drag on the loping, jump-rope, thread which is passing through the eye. Where, as here, the thread is an elastomeric fiber such as spandex thread, which is bare and substantially free of finish, the fiber-to-fiber and fiber-to-ceramic frictional characteristics are significantly higher than with covered or lubricated fibers. Thus, a significant drag results when this very tacky thread is pulled across the static ceramic surface of the eye guide. The rotational ballooning action of the thread, as the thread is pulled from the package, causes the thread to be dragged along the edges of the ceramic eye guide rather than straight through the center of the eye. The frictional drag, between the static eye and the tacky thread, is exacerbated as the angle of wrap of the thread around the edge of the static eye guide is increased. Because of the jump-roping motions, the angle of contact with the static ceramic eye is constantly changing. Therefore, the amount of friction at the static eye is constantly changing, resulting in alternating large and sudden increases and decreases in tension, and accompanying sticking and slipping of the thread at the ceramic eye. The resulting friction is neither constant nor predictable, whereby the thread is also experiencing ongoing and constant substantial changes in speed of advance of the thread along the thread path.
While this invention is capable of handling a wide variety of thread types, the advantages of this invention are readily experienced in handling unwind and transport of untreated elastomeric fiber thread. Such elastomeric fiber thread is uncoated, having no lubricant, no oil on its surface. The thread can be an “as spun” thread, or a rewound thread. The rewound thread has a much more consistent drag, tension as it is unwound from the spool, than an “as spun” thread. The thread has a size in the range of about 200 decitex to about 2000 decitex, typically about 400 decitex to about 1000 decitex.
Typical tension in the thread as it leaves the package can be as little as about 2 grams for a rewound thread. For an as-spun thread, the tension as the thread leaves the package typically averages about 5 grams to about 20 grams. However, the tension varies substantially depending on stage of the unwind at which the tension is being measured. For example, where the average tension e.g. over a 10 minute period is measured as 6 grams at the outside of the package, e.g. when unwinding of that package has just started, the average tension just before the unwinding reaches the core or end of the package is substantially higher such as 12 grams.
When real-time tension is measured in very short increments such as at 0.1 second increments, thread-to-thread sticking reveals substantially greater spikes in tension differences, from a tension of effectively zero to a tension as high as 3040 grams or higher, all in the course of e.g. releasing a single wrap from the spool.
The overall objective of the thread feed is to convert a roll of wound up elastomeric fiber thread, from a highly variable tension as the thread leaves the spool, to a thread which feeds into the manufacturing nip at a constant and controllable tension of about 80 grams to about 250 grams, depending on the thread decitex and the finished manufacturing product specifications.
Thus it is desired to provide an overend thread unwind system for elastomeric and tacky threads which is effective to capture the loping, jump rope, activity of the thread as the thread is unwound from the spool.
It is a further desire to capture the loping, jump rope, activity of the thread while applying a minimal amount of friction and/or drag force on the thread.
It is still further desirable to capture the loping, jump rope, thread with a travelling e.g. rotating or rolling, capture device, such that the thread does not necessarily routinely travel over any static surfaces.
It is further desirable to capture the loping, jump rope thread with rotating devices which are closed on opposing ends of the device such that the thread cannot come off the capture device by moving laterally along the axis of rotation of the device and past the end of the device, and whereby the thread will be prevented from moving off the device by the end closure structure.
It is yet further desirable to exert a first-stage tension control input on the thread at the unwind creel close to the elastic thread package and to exert a second-stage tension control input on the thread proximate the manufacturing nip, and whereby the thread traverses no more than a minimal number of thread guides, if any, between the second tensioning device and the manufacturing nip.
It is still further desirable to provide a manufacturing operation wherein a tacky thread is fed into the product assembly operation at a constant tension, controlled by an unwind and feed system which exerts a final tension control on the thread at an up-stream location proximate the entrance of the thread into the product assembly operation, such that the thread typically experiences no more than three, optionally no more than one or two, guide surfaces after departing the final tensioning device, and wherein the final tensioning device is no more than three meters, optionally no more than one or two meters, from entrance of the thread into the manufacturing nip.
Tensioning devices such as the BTSR brand KTF-RW constant tension feeder are typically used as stand-alone devices. Parameters such as tension setpoint, tension deviation alarm window, system responsiveness/reactivity, etc. are usually set at each individual device. Dynamic status values such as tension feedback, drive current, drive temperature, and system health status are usually only available for display on each tensioning device drive module.
Hand-held programming devices and PC-based software systems exist which can be used for the initial setup of the tensioning devices. However none of such devices provide for integration of the tensioning devices with the industrial programmable logic controllers (PLC's) which are standard in automated manufacturing processes.
Standard practices and controls procedures for most automated industrial manufacturing processes, especially in the personal care industries, such as the hygiene industry, the baby diaper industry, and the adult incontinent industry, require complete integration of all devices and sub-systems which participate in the manufacturing operation. All operating parameters for all devices in the entire manufacturing line must be set and monitored from a central operator interface, usually a touch screen, which in turn is connected to the central PLC. The central PLC manages all of the setpoint parameters and monitors feedback and status data from all devices on the production line.
Conventional, off-the-shelf tensioning devices require direct or local input of control parameters into the individual devices, and thus do not conform to such centralized control scheme, and are therefore prohibited from use in many manufacturing environments. There is a need for a means to fully integrate the control and monitoring of setpoints, feedback, and status values of tensioning devices into an automated manufacturing system.
Production lines used in the manufacture of hygiene, baby diaper, adult incontinent, and related products are complex, with highly sophisticated control systems. Due to the complexity of the programming in the main system PLC, it is a difficult, time-consuming, and expensive process to make significant program changes to a functioning production line. Therefore, when the new accessory or sub-system, namely the elastic feeding equipment of the invention is added to the production line, it is generally preferable for the time-critical functions of such sub-system to be handled by a secondary controller which then communicates with the main PLC. Setpoint information for the subsystem is sent to the secondary controller from the main PLC. Feedback and status information are sent from the secondary controller to the main PLC.